For the power or speed regulation of turbines, particularly those operating on compressible fluid, such as steam or gas, often sectional nozzles are used, the inlet of which is conventionally governed by valves. A separate valve is provided for each of the nozzle sections and an appropriate cam shaft actuating device is necessary for the positioning of the different valve stems. Such an arrangement is relatively expensive and needs skillful adjustment of the cam shaft.
Further, each valve normally consists of a stem, which must be sealed from the atmosphere, a valve element which is fixed to or connected with the stem and which must fit exactly into its own seat, so that no fluid flow is admitted to the turbine by the respective valve in the closed state.
In order to actuate the stem of the valves, either large forces are often necessary or duplex poppet valves or balanced steam admission valves are used. The latter are of expensive construction.
It is therefore an object of the invention to provide a sectional nozzle control valve which needs only small actuating forces.
It is a further object of the invention to reduce the number of valve stems and cam devices, more particularly, to reduce the number to only one each or none at all regarding the cam devices, regardless of the number of nozzle sections.
It is also an object of the invention to provide a sectional nozzle control valve which is neither bulky nor expensive but nevertheless ensures a precise nozzle control.